Flat Top

In a recent discussion with a fellow racer I was quite surprised when he indicated to me that a "Porsche guru" had indicated to him that when building a cage into your car you do not want to have the chassis too stiff. In fact, he said, that you actually want flex in the rear chassis. "Many guys make their car too stiff." he said.

The guy that told me this tale is a newbie to building cars and he is looking around for advice from many different sources.

I was surprised and tried to explain that (IMHO) a chassis should be as rigid as possible to allow the suspension to do its own work - especially as you go stiffer on springs.

I posted this for you to indicate whether a stiff chassis, in your opinion, is more desireable that a flexing chassis. (I will then direct him and the "Porsche guru" here to read your opinions). Hopefully I will not have egg on my face!

Thanks guys.

Johan

sweanders

If the chassis is not stiff enough you will have a very hard time setting up the suspension since it might be stiffer than the body. On 996 Cup cars it can be a problem setting the swaybars to stiff since the swaybar will be stiffer than the body flex.

RedlineMan

Indeed;

It is well known that you want a chassis as stiff as possible. Suspension tuning is all about variables. At the track, you can tune the suspension, but you can not tune the chassis, so you want to eliminate that variable. Otherwise, you are litterally chasing a moving target. At some point you will make a setting change, but see no effect, or not the effect you know from experience should be the result. You keep tuning, but your results are not linear like they are on a stiff chassis. When you can't get the result you expect, you are then lost and guessing.

Stiff is best.

SeaCay

It's really just too easy to take a swing at this one...

Bill L Seifert

Quote: "It's really just too easy to take a swing at this one..."

What does that mean?

There is no question, Stiff is best. Look at Indy Cars, F1, etc, etc. You don't want the chasis to be a spring. It's impossible to adjust.

Bill Seifert

1987 944S Race Car

Larry Herman

Bill, you're thinking with the wrong head.

sjanes

As someone that drives a Targa with a stiff suspension on the track, I have to agree with John. If I run the sway bars too stiff, the handling gets a little weird.

Alan C.

Thanks Larry, you made my morning

chrisp

Also, chassis flex is undamped and therefore uncontrolled.

Bill L Seifert

You know, I just now got it. Duhhhhhhhhh!!!!!!!!

Bill

gbaker

We were worried about you, Bill.

Gregg

JCP911S

"Porsche guru" is often just the guy with the biggest mouth.... chassis cannot be too stiff IMHO

38D

Q: How stiff do you want your chassis?
A: Stiffer than Ron Jeremy at the Playboy Mansion.

Larry Herman

You are right, on both counts. I remember back in the day when Holbert Racing was running the D production cars (924 turbos I think??) and there was always a clash between the Germans who prefered lighter weight at the expense of chassis stiffness, and the Americans who wanted rock stiff chassis, regardless of any weight penalty. The American built cars were faster because they handled better.

RedlineMan

Oh Bruddah!

Two different cases of not getting "IT" one might surmize. What a hoot!

Anyone with a pre 964 911 chassis that ran much North of 500lb springs has learned this lesson... hopefully. You keep adjusting and nothing happens. The springs aint moving, the CHASSIS is. Targas are worse, of course.